Custom Special / ODR-CS Overdrive

ODR-CSAfter I finished developing the ODR-1 at the end of 1992 (for Nobels), we wanted to launch an "enhanced" model with a 3-band tone control. I took my overdrive circuit out of the ODR-1 and modified a few stages. For example 3-band tone control and distortion with germanium diodes!

That might have happened a bit quickly back then - because nowadays I would have liked to have designed a few details differently, or rather I have done so.

Note: The ODR-CS is different from the ODR-C and therefore has a different sound!

Here is the shop!


What I improved:

  • Conversion to true bypass operation
  • Best Components:
    • 1% metal film resistors.
    • Maximum 5% film capacitors (Wima, Epcos, Kemet) in the signal path.
  • Solid 6.3mm gold plated cliff sockets (UK).
  • Gold-plated PCB plugs / sockets
  • High quality, screwed large potentiometers.
  • Special foot switch with an extra light pressure point.
  • Small G.D.C. potentiometer.
  • Improved bass and treble controls.
  • Extended middle adjustment range (previously only +mids, now +/-mids).
  • Adjustable LED brightness (internal).
  • Smaller, stable and closed aluminum housing from Hammond Mfg./UK (perfect shielding against hum and EMC)
  • Massive design such as screwed boards with double gold-plated contacts between the main and controller boards.
  • 9 to 18 volt operation. Other tones are possible by operating with voltages between 9 V and 18 V. Difficult to explain: Just try it! The feel of the game changes.


 Block Diagram

ODR CS Blockdiagram DE V2

  • At the input is the capacitor-free JFET input stage, which converts the sensitive high-impedance signal into a low-impedance one.
  • A small filter stage follows, which feeds the signal into the overdrive stage.
  • The overdrive stage runs with silicon diodes - a classic overdrive principle. The strength of the overdrive can be adjusted with the Drive control.
  • Like the ODR-C, the ODR-CS has a soft-clipping overdrive stage, followed by a hard-clipping (distortion) stage. In contrast to the ODR-C, the ODR-CS uses germanium diodes instead of silicon diodes. Germanium diodes have a different - more flatter characteristic - and sound correspondingly different. The germanium diodes limit the signal and add many harmonics. I did this with the G.D.C. Controller (Germanium Drive Control) made adjustable so that the proportion of harmonics can be reduced. This is particularly well suited for low gain operation.
  • The following is the 3-band equalization (EQ):
    • In contrast to the 1993 version, I have slightly revised the bass and treble controls.
    • The mid control, which previously could only add mids, can now also subtract mids. That expands the function!
  • Finally comes the output filter to adjust the sound as well
  • The volume control and finally followed by the
  • Output impedance converter


Drive Knob / G.D.C. Knob

With the drive controller you set the strength of the overdrive. With little drive, the overdrive distortion is very low, so the G.D.C. knob dominates the tone or amount of distortion. For example G.D.C. on left: maximum germanium distortion. Or G.D.C. on the right: minimal germanium effect (hardly any distortion!), so here a pretty clean sound is audible.

If the drive control is turned up wide, with the G.D.C. regulator then you get a nice silicon overdrive!

Compared to the ODR-S from 1993, I have reduced the control range of the drive controller somewhat, firstly because hardly anyone plays with maximum drive and secondly because the controller can now be set much more sensitively in low-gain mode.

Note: Germanium diodes limit the output level, the more they work. Then correct the volume with the level control if necessary!


Example: Settings for Drive/G.D.C.

  Funktion    Drive    G.D.C.  
  Low Gain / Booster          
 Germanium Overdrive          
 Germanium / Silizium Overdrive          


 Silicon Overdrive          

A note on germanium diodes:
Germanium diodes have a temperature-dependent characteristic. As a result, they also sound a little different at higher or lower temperatures (e.g. winter or summer). This is typical and normal.


The 3-Band Equalizer


  • Red: Bass +
  • Blue: Bass center
  • Orange: Bass -

CS Bass



  • Gray: Mid +
  • Blue: Mid center
  • Green: Mid -

 CS Mid



  • Cyan: Treble +
  • Blue: Treble center
  • Purple: Treble -

 CS Treble


*Note: The ODR-CS is absolutely not 1:1 comparable to the controller positions of the ODR-S (1993)! If only for the reason that the Mid controller can now also be adjusted (Mid -)!


Technical Data*

  • Input Impedance ~1 MΩ
  • Output Impedance ~1 kΩ
  • Power supply with DC 9 V battery:
    • Dry battery 6F22 (9 V)-Type (Carbon)
    • Dry battery 6LR61 (9 V)-Type (Alkali-Manganese)
  • Battery life during continuous operation*):
    • Carbon: 20 hours (calculated with a battery capacity of 300mAh)
    • Alkaline manganese: 33 hours (calculated with a battery capacity of 500mAh)

*) This information depends on the battery and the ambient conditions!

  • DC power supply 9 V to 18 V (electronically stabilized)
  • Power consumption: approx. 15 mA at 9 V, approx. 25 mA at 18 V
  • Dimensions 125 (L) x 66 (W) x 58 (H) mm
  • Weight ca. 360 g (without Battery)

*Technical and written changes reserved!


The development of the ODR-CS

In the last few years I have seen again and again that some musicians in the USA had "rehoused" the ODR-S: In other words, they had put the ODR-S in a different housing and instead of the FET effect switching that was common at the time, into one True bypass switch rebuilt. I then also had contact with some musicians and was able to experience the strengths and weaknesses of the "S". From this, the interest grew to "revive" the ODR-S.

That wasn't easy at all... because the old ODR-S from 1993 had special germanium diodes installed. By the way, they weren't AA-112s, as it says in the circuit diagrams that are in circulation!
(Actually, it was my fault - since I didn't even have the actual diodes in my schematic software and I used the AA-112 instead. Oops!)

Unfortunately, these diodes were replaced with others in the later (Nobels) editions (silver or black housing) of the ODR-S - as the original ones were no longer available. However, these had a different sound - which I didn't like that much anymore. But what should you do then? It was supposed to be produced... the one about "history".


Feasible or not?

So it should be the 1993 variant. So I started looking for suitable germanium diodes. I got myself a characteristic curve recorder and analyzed the original diodes. I still had several of the old ODR-S in stock as samples. After a number of "purchases" of various samples, I found some that pretty much matched the original characteristics. A sound check confirmed the good qualities. Unfortunately, I did not find enough germanium diodes (in 2020) and had to stop development for the time being.

About a year later I found by chance an auction with a stock clearance, where exactly my desired germanium type was contained. Now I had a few thousand diodes in stock. And less than two weeks later I found about 3000 more pieces at another auction... The starting shot had been fired!


 Originally packed germanium diodes!

It is well known that germanium diodes have a high spread of the characteristic curve. Apart from that, the characteristic curve even changes depending on the ambient temperature. One of the reasons why they were later replaced by more stable silicon diodes. Nowadays, germanium diodes are hardly manufactured anymore. Too bad for the music world :-(

I decided to measure and classify the germanium diodes in pairs (characteristic curve). This of course reduces the number of available diodes. Since I have enough in stock, I should still be able to build enough ODR-CS for the next few years. So look forward to it!


Table of Differences

 Function ODR-S
 True-Bypass - X
 9 - 18 V operation - X
 Screwed jacks - X
 Screwed potentiometers - X
 G.D.C. knob - X
 Adjust. LED brightness - X
 Batterie operation X X
 Remote jack X -



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